This invention relates to improvements in equipment for chemical, food and other material treatment in laboratories and the like, and is directed particularly to improvements in leakage preventing seals and especially seals or sealing means associated with stirring equipment.
In many operations performed in laboratories the stirring of materials in sealed flasks is carried out. In these stirring operations a stirring rod of glass or the like may pass through the neck of the flask and carry a stirring blade means on its lower end within the flask, while the outer or upper end of the rod is connected with a suitable source of power for rotating the rod. Since the flasks under certain conditions must be kept tightly sealed or closed while such a stirring operation is being carried out, a seal must be maintained at all times between the rotating stirring rod and a seal or closure member in the mouth or neck of the flask to prevent liquids or vapors creeping along the stirring rod or shaft and escaping from the flask, where the flask may be kept under pressure from within during the stirring operation, and it is also important that such a seal be maintained to prevent the passage of dust or other material along the stirring rod and into the flask, on those occasions where a reduced pressure may be maintained in the flask.
There are many types of seals in use in the prior art for effecting liquid tight seals between stirring apparatus and a flask, and one type of such prior art seal as used in vacuum desiccating equipment utilizes a sealing fluid, such as mercury, for example. This is objectionable in the carrying out of certain operations, such as in the performance of distillation operations connected with the production of food or the like, or in other instances wherein the use of mercury would constitute a hazard. Also, the use of such seals creates excessive torsional forces which places strain upon rotating elements of the stirring apparatus. Other prior art devices utilize mechanical seals wherein various plastic elements in combination with metallic elements are used, and in fact, in those instances wherein a high number of revolutions per minute is required over a long period of time, metal components may be used. However, these seals are not satisfactory, since galling of metal or glass materials frequently occurs and the seal is thus destroyed or excessive pressures are required in order to effect a seal between the diverse materials, with the result that additional power is required in order to operate the stirring apparatus. Moreover, these prior art seals do not have means for enabling manual adjustment of the sealing pressure exerted on the rod of the stirring apparatus.